1. Field of the Invention
This invention relates to an optical quantizing unit and an optical A/D converter, and more particularly relates to an optical quantizing unit which produces optical pulses whose quantities are proportional to intensities of input optical pulses, and an optical A/D converter provided with the optical quantizing unit.
2. Description of the Related Art
U.S. Pat. No. 4,712,089 discloses an optical quantizing circuit which produces optical pulses in proportion to the intensity of optical pulses.
In Reference 1, input optical pulses to be quantized are divided in accordance with the number of quantizing levels, and the optical pulses to be quantized are input into a plurality of optical threshold filters having different threshold values.
The optical threshold filters compare the optical pulses to be quantized with threshold values, and output optical pulses when the optical pulses to be quantized have light intensities above the threshold values. The number of the outputted optical pulses is proportional to intensities of optical pulses to be quantized.
However, since the foregoing optical threshold filters are large, the optical quantizing unit inevitably become bulky as a whole. Further, when a plurality of optical threshold filters are provided, the application efficiency of light will be lowered, and intensities of the input optical pulses to be quantized will be increased. Therefore, it is difficult to fabricate an economical optical quantizing unit.